1. Field of the Invention
This invention relates to a ultrahigh tenacity, ultrahigh modulus polymer alloy fiber consisting of a wholly aromatic polyamide polymer and a regularly ordered aromatic-aliphatic copolyamide polymer.
2. Prior Art
When para-oriented wholly aromatic polyamide polymers, for instance, poly(p-phenylenephthalamide), poly(p-benzamide) and the like are dissolved in a tertiary amide solvent or concentrated sulfuric acid at a high level of concentration, they form liquid crystals. Particularly, when such polymers with a high degree of polymerization are spun in the liquid crystalline state, it is possible to obtain ultrahigh tenacity and modulus fibers. The techniques of this type were disclosed in U.S. Pat. Nos. 3,671,542, 3,869,429, and 3,869,430 and have now been industrialized. Their products also are commercially available.
The ultrahigh tenacity and modulus properties of para-oriented wholly aromatic polyamide fibers are considered attributed to the facts that the molecular chains constituting such fibers are in rigid rod-like forms and that the molecules of the fibers are extraordinarily well ordered in parallel as compared with those of the fibers with common flexible aliphatic molecular chains. These fibers with rod-like molecular chains exhibit very high tensile strength and modulus in the direction of the fiber axes but very low mechanical strength in the direction perpendicular to the fiber axes; this is due to the fibrillation of the fibers. The fibrillation is a severe drawback in para-oriented wholly aromatic polyamide fibers and, as mentioned above, is ascribed to the fact that the molecular chains of the fibers are in the rigid rod-like forms and have a fibril-like orientation. Thus, under conditions that a load or friction is repeatedly applied, the fibers are apt to be split into a number of individual fibrils, causing their tenacity and modulus deteriorated fatally. These defects may cause the use of ultrahigh tenacity and modulus fibers considerably restricted. Accordingly, many studies to improve the defects have worldwide been being made.